The subject matter of this invention is related to the disclosure of German published patent Application No. 1,119,726 and serves to prevent a premature unblocking, for example, during an ignition delay. The arrangement includes a spring-loaded recoil arresting lever in a breech body for purposes of coacting with a blocking head. There is also, axially slidably disposed in the breech body a blocking slider and a blocking-weight; a coil spring is arranged between the latter two. This prior art arrangement requires a large amount of coaction of predetermined parts, which must be coordinated in accordance with their mass and the frictional forces which occur between non-locking, non-irreversible stop surfaces in accordance with the forces exerted by the corresponding spring and in accordance with the corresponding intertia moments of the various parts. The large number of individual parts has been found to be disadvantageous, because they constitute a complex constructional assembly and, in view of the high velocity and acceleration, to which the assembly is exposed, constitutes not only a very large assembled mass, which is a drawback, but also such complex construction produces significant malfunctionings.